1. Field
An aspect of one embodiment of the present invention is directed to an organic light emitting display, and a driving method thereof.
2. Description of Related Art
Various flat panel displays with reduced weight and volume in comparison to a cathode ray tube display have been developed. The various flat panel displays include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), an organic light emitting display, etc.
Among the various flat panel displays, the organic light emitting display, which displays an image using organic light emitting diodes (OLEDs) that light-emit light by a re-combination of electrons and holes, has a rapid response speed and low power consumption.
Generally, organic light emitting displays can be classified as a passive matrix type OLED (PMOLED) display and an active matrix type OLED (AMOLED) display according to a method of driving the OLEDs.
The AMOLED display includes a plurality of gate lines, a plurality of data lines, a plurality of power lines, and a plurality of pixels that are coupled to the lines and arranged in a matrix form. Also, each of the pixels generally includes an OLED, two transistors, e.g., a switching transistor that transfers a data signal and a driving transistor that drives the OLED according to the data signal, and a capacitor that maintains the data voltage.
The AMOLED display has low power consumption, but the amount of currents flowing through its OLEDs vary according to deviations in threshold voltage of its transistors to cause display non-uniformity.
In other words, since the characteristics of the transistors provided in each pixel are changed according to variables in their manufacturing processes, it is difficult to manufacture the transistors so that the characteristics of all of the transistors in the AMOLED display are identical, thereby causing deviations in the threshold voltage between the pixels.
A compensation circuit that includes a plurality of transistors and capacitors can be additionally included in the respective pixels. However, the additional compensation circuit causes additional transistors and capacitors to be added in each pixel.
If the compensation circuit is added in the respective pixels as described above, the transistors and capacitors that constitute each pixel and the signal lines that control the transistors are added so that in a bottom emission type AMOLED display, an aperture ratio is reduced, and the probability that defects are generated is increased due to the increased complexity of the circuit.
Moreover, there is a recent demand for a high-speed scan driving of 120 Hz or more in order to reduce or eliminate the screen motion blur phenomenon. However, in this case, a charging time available for each scan line is significantly reduced. In other words, when the compensation circuit is provided in each pixel so that a plurality of transistors are additionally provided in each pixel coupled to one scan line, its capacitive load becomes larger, such that the high-speed scan driving is difficult to be implemented.